U.S. patent application number 13/269076 was filed with the patent office on 2012-10-18 for base metal alloys with improved conductive properties, methods of manufacture, and uses thereof.
This patent application is currently assigned to UNIVERSITY OF CONNECTICUT. Invention is credited to Mark AINDOW, S. Pamir ALPAY, Joseph V. MANTESE.
Application Number | 20120263971 13/269076 |
Document ID | / |
Family ID | 44906382 |
Filed Date | 2012-10-18 |
United States Patent
Application |
20120263971 |
Kind Code |
A1 |
AINDOW; Mark ; et
al. |
October 18, 2012 |
BASE METAL ALLOYS WITH IMPROVED CONDUCTIVE PROPERTIES, METHODS OF
MANUFACTURE, AND USES THEREOF
Abstract
A composition comprises a binary alloy of iron and one of
manganese, molybdenum, or vanadium, wherein the manganese,
molybdenum, or vanadium is present in the binary alloy in an amount
effective to form a conductive oxide on the binary alloy, the
oxidation state of the manganese, the molybdenum, and the vanadium
is greater than the oxidation state of iron in the conductive
oxide, and the conductive oxide has a contact resistance of less
than 5.times.10.sup.4 milli-ohms measured in accordance with ASTM
B667-97 (2009).
Inventors: |
AINDOW; Mark; (Tolland,
CT) ; ALPAY; S. Pamir; (South Windsor, CT) ;
MANTESE; Joseph V.; (Ellington, CT) |
Assignee: |
UNIVERSITY OF CONNECTICUT
Farmington
CT
|
Family ID: |
44906382 |
Appl. No.: |
13/269076 |
Filed: |
October 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61512613 |
Jul 28, 2011 |
|
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61404764 |
Oct 8, 2010 |
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Current U.S.
Class: |
428/681 ;
148/284; 420/120; 420/123; 420/127; 420/72; 420/8; 428/457 |
Current CPC
Class: |
C22C 38/04 20130101;
C22C 38/12 20130101; C22C 38/00 20130101; Y10T 428/31678 20150401;
Y10T 428/12951 20150115 |
Class at
Publication: |
428/681 ;
148/284; 420/72; 420/120; 420/123; 420/127; 420/8; 428/457 |
International
Class: |
H01B 1/02 20060101
H01B001/02; B32B 15/01 20060101 B32B015/01; C22C 38/12 20060101
C22C038/12; C23C 8/00 20060101 C23C008/00; C22C 38/04 20060101
C22C038/04 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] This invention was made with government support under Grant
No. W-911-NF0710388 awarded by the U.S. Army Research Office. The
government has certain rights in the invention.
Claims
1. A composition comprising a binary alloy of iron and one of
manganese, molybdenum, or vanadium, wherein the manganese,
molybdenum, or vanadium is present in the binary alloy in an amount
effective to form a conductive oxide on the binary alloy, the
oxidation state of the manganese, molybdenum, and vanadium is
greater than the oxidation state of the iron in the conductive
oxide, and the conductive oxide has a contact resistance less than
5.times.10.sup.4 milli-ohms measured in accordance with ASTM
B667-97 (2009).
2. The composition of claim 1, wherein the manganese is present in
an amount from 1 at. % to 10 at. % Mn.
3. The composition of claim 2, wherein the manganese is present in
an amount from 1 at. % to 5 at. % Mn.
4. The composition of claim 3, wherein the manganese is present in
an amount from 3 at. % to 5 at. % Mn.
5. The composition of claim 1, wherein the molybdenum is present in
an amount from 1 at. % to 10 at. % Mo.
6. The composition of claim 5, wherein the molybdenum is present in
an amount from 1 at. % to 5 at. % Mo.
7. The composition of claim 6, wherein the molybdenum is present in
an amount from 1 to 3 at. % Mo.
8. The composition of claim 1, wherein the vanadium is present in
an amount from 1 at. % to 30 at. % V.
9. The composition of claim 8, wherein the vanadium is present in
an amount from 4 at. % to 20 at. % V.
10. The composition of claim 9, wherein the vanadium is present in
an amount from 8 at. % to 12 at. % V.
11. The composition of claim 1, wherein the binary alloy is a
single phase.
12. The composition of claim 1, wherein the binary alloy is a solid
solution of the manganese, molybdenum, or vanadium in the iron.
13. The composition of claim 1, wherein the binary alloy has a bulk
resistivity from 25 nano-ohm-meters to 500 nano-ohm-meters.
14. The composition of claim 1, wherein the binary alloy has a bulk
resistivity from 50 nano-ohm-meters to 500 nano-ohm-meters.
15. The composition of claim 1, further comprising the conductive
oxide of the binary alloy.
16. The composition of claim 15, wherein the conductive oxide is a
single phase, and the manganese, molybdenum, or vanadium is
substitutionally incorporated into a lattice of the conductive
oxide.
17. The composition of claim 16, wherein a contact resistance of
the composition is less than 5.times.10.sup.4 milli-ohms.
18. The composition of claim 15, wherein the manganese, molybdenum,
or vanadium in the conductive oxide is present in an amount
effective to change a relative amount of Fe.sup.2+ and Fe.sup.3+ in
the conductive oxide.
19. A process of making the binary alloy of claim 1, comprising
alloying iron and one of manganese, molybdenum, or vanadium to form
the binary alloy.
20. A process of making the composition of claim 1, comprising:
alloying iron and one of manganese, molybdenum, or vanadium to form
the binary alloy; and maintaining the binary alloy under a
condition effective to oxidize at least a portion of the binary
alloy to form the conductive oxide.
21. An electrical device comprising: a first component and a second
component in a spaced apart relation; and the composition of claim
1 disposed between and in physical contact with the first component
and the second component, wherein the composition completes an
electrical path between the first component and the second
component.
22. An electrical device comprising: a metal substrate; and a
coating comprising the composition of claim 1 disposed on the metal
substrate and in electrical contact with the metal substrate.
23. The electrical device of claim 22, further comprising a
metallic member to electrically contact the coating.
24. The electrical device of claim 23, wherein the electrical
device is a blade connector, push-on connector, crimp connector,
multi-pin connector, bolt connector, set screw connector, lug,
wedge connector, bolted connector, compression connector, coaxial
connector, wall connector, surface mount technology board
connector, IPC connector, DIN connector, phone connector, plastic
leaded chip carrier socket or surface mount connector, integrated
circuit connector, ball grid array connector, staggered pin grid
array connector, or bus bar connector.
25. The electrical device of claim 23, wherein the electrical
device is a circuit breaker, mercury switch, wafer switch,
dual-inline package (DIP) switch, reed switch, wall switch, toggle
switch, in-line switch, rocker switch, microswitch, or a rotary
switch.
26. An article comprising the electrical device of claim 20.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 61/512,613, filed Jul. 28, 2011, and
U.S. Provisional Patent Application Ser. No. 61/404,764, filed Oct.
8, 2010, which are both incorporated by reference herein in their
entirety.
BACKGROUND
[0003] Electrical contacts are used in many devices for current
delivery between components. In many applications, a transition
metal is selected as a base metal of the electrical contact, and a
thin layer of a precious metal, e.g., gold, silver, or platinum, is
plated on the base metal. The precious metal layer is used to
maintain a relatively low contact resistance of the electrical
contact and its mating contact. High contact resistance can lead to
open circuit characteristics that impede current flow. Further, the
contact resistance of the base metal can increase over time leading
to device failure. Beyond electrical failure, increasing contact
resistance can cause increased local heating and thermal problems
in devices.
[0004] One source of increased contact resistance is the formation
of metallic oxides at the contact surfaces. For example, mechanical
vibration or different thermal expansion rates of the electrical
contact and its mate can cause relative movement of the electrical
contact. Such movement can be abrasive, exposing the base metal of
the contact that is then subject to oxidation. Because the oxidized
debris can be much harder than the surfaces from which it came, it
can act as an abrasive agent that increases the rate of both
fretting and mechanical wear. As more fresh base metal is exposed
and oxidized, the contact resistance increases, and electrical
failure can occur.
[0005] Precious metals are generally used to decrease the oxidation
rate of the base metal in an electrical contact. However, precious
metals are costly and can be difficult to procure. There
accordingly remains a need in the art for materials and methods
that decrease the oxidation of the base metal in an electrical
contact.
SUMMARY
[0006] Disclosed herein is a composition comprising a binary alloy
of iron and one of manganese, molybdenum, or vanadium, wherein the
manganese, molybdenum, or vanadium is present in the binary alloy
in an amount effective to form a conductive oxide from the binary
alloy, the oxidation state of the manganese, molybdenum, and
vanadium is greater than the oxidation state of the iron in the
conductive oxide, and the conductive oxide has a contact resistance
of less than 5.times.10.sup.4 milli-ohms measured in accordance
with ASTM B667-97 (2009).
[0007] In a specific embodiment, the composition further comprises
the conductive oxide of the binary alloy.
[0008] Also disclosed herein is a process of making a binary alloy
comprising alloying iron and one of manganese, molybdenum, or
vanadium to form the binary alloy.
[0009] In addition, disclosed herein is a process of making a
composition comprising a binary alloy and a conductive oxide of the
binary alloy, the process comprising alloying iron and one of
manganese, molybdenum, or vanadium to form the binary alloy; and
maintaining the alloy under a condition effective to oxidize at
least a portion of the binary alloy to form the conductive
oxide.
[0010] An electrical device comprises a first component and a
second component in a spaced apart relation; and the binary alloy
or the composition comprising the binary alloy and the conductive
oxide of the binary alloy disposed between and in physical contact
with the first component and the second component, wherein the
binary alloy or the composition completes an electrical path
between the first component and the second component.
[0011] The above described and other features are exemplified by
the following figures and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Referring now to the figures, which are embodiments, and
wherein like elements are numbered alike:
[0013] FIG. 1 is a cross-section of an embodiment of a binary alloy
of Fe--X with a conductive oxide (Fe,X).sub.3O.sub.4 scale;
[0014] FIG. 2 is a model of electron/polaron hopping in an
embodiment of a conductive oxide of a binary alloy;
[0015] FIG. 3 is a secondary electron scanning electron microscope
image of an embodiment of an Fe--V alloy;
[0016] FIG. 4 is a graph of relative intensity (arbitrary units,
a.u.) versus scattering angle (degrees, 2.theta.) data from an
X-ray diffraction pattern of an embodiment of a conductive oxide of
an Fe--V alloy;
[0017] FIG. 5 is an electron diffraction pattern of the conductive
oxide of the Fe--V alloy corresponding to the data shown in FIG.
4;
[0018] FIG. 6 is a graph of contact resistance (milli-ohms,
m.OMEGA.) versus oxidation time (hours, hr) for a Cu sample, an Fe
sample, and an embodiment of a conductive oxide of an Fe-8V
alloy;
[0019] FIG. 7 is a phase diagram of temperature (degrees Celsius,
.degree. C.) versus weight percent V (wt. % V) and atomic percent V
(at. % V) for an Fe--V system;
[0020] FIG. 8 is a graph of contact resistance (milli-ohms,
m.OMEGA.) versus oxidation time (hours, hr) for a Cu sample, an Fe
sample, and an embodiment of a conductive oxide of an Fe-4V alloy,
Fe-8V alloy, Fe-12V alloy, Fe-16V alloy, and Fe-20V alloy;
[0021] FIG. 9 is a phase diagram of temperature (degrees Celsius,
.degree. C.) versus weight percent Mn (wt. % Mn) and atomic percent
Mn (at. % Mn) for an Fe--Mn system;
[0022] FIG. 10 is a graph of contact resistance (milli-ohms,
m.OMEGA.) versus oxidation time (hours, hr) for a Cu sample, an Fe
sample, and an embodiment of a conductive oxide of an Fe-1Mn alloy,
Fe-2Mn alloy, Fe-3Mn alloy, Fe-4Mn alloy, and Fe-5Mn alloy;
[0023] FIG. 11 are phase diagrams of temperature (degrees Celsius,
.degree. C.) versus weight percent Mo (wt. % Mo) and atomic percent
Mo (at. % Mo) for an Fe--Mo system; and
[0024] FIG. 12 is a graph of contact resistance (milli-ohms,
m.OMEGA.) versus oxidation time (hours, hr) for a Cu sample, an Fe
sample, and an embodiment of a conductive oxide of an Fe-1Mo alloy,
Fe-2Mo alloy, Fe-3Mo alloy, Fe-4Mo alloy, and Fe-5Mo alloy.
DETAILED DESCRIPTION
[0025] The inventors hereof have discovered that a limited number
of binary alloys, in particular binary alloys containing iron and a
specific amount of one of manganese, molybdenum, or vanadium can
form conductive oxides. The binary alloys are highly useful as
electrical contacts, where oxidation of the electrical contact
using prior art materials ordinarily forms a non-conductive oxide.
The production of non-conductive oxides can severely limit the
performance and/or life of an electrical device. In some instances,
formation of a non-conductive oxide can compromise the safety of
the device. Use of the inventive binary alloys can therefore
improve one or more the performance of an electrical device over
time, increase the lifetime of the device, or improve the safety of
the device. Use of the inventive binary alloys further provides a
lower cost alternative to prior art electrical contact materials
because the binary alloys are not required to be coated with a
precious metal, e.g., gold, silver, or platinum. The binary alloys
can therefore decrease the use of precious metal plating of
electrical contacts while conserving the operational
characteristics of such current-carrying contacts.
[0026] In an embodiment, binary alloys are described that contain
two elements: iron and one of manganese, molybdenum, or vanadium in
specified amounts. For convenience, these binary alloys can be
referred to herein as Fe--V, Fe--Mn, and Fe--Mo, or generally as
Fe--X with X being manganese, molybdenum, or vanadium. As is known
to those of skill in the art, the materials used in the manufacture
of alloys often contain low levels of various impurities,
particularly metal-, carbon-, or nitrogen-containing impurities.
Such impurities can be present in the binary alloys described
herein, provided that such impurities are not present in an amount
that significantly adversely affects the desired properties of the
alloys, in particular the formation of a conductive oxide.
Impurities may be present in the binary alloy in minor amounts due
to, for example, the inherent properties of iron, manganese,
molybdenum, or vanadium or may be present due, for example, to
leaching from contact with manufacturing equipment or uptake during
processing of the binary alloy. For example, the binary alloys can
contain less than 1 weight percent (wt. %), less than 0.5 wt. %, or
less than 0.1 wt. % of materials other than the iron and one of
manganese, molybdenum, or vanadium, based on the total weight of
the binary alloy.
[0027] In order to obtain a binary alloy that forms a conductive
oxide, the amount of iron and the manganese, molybdenum, or
vanadium are carefully adjusted.
[0028] The Fe--Mn binary alloy contains manganese in an amount from
1 atomic percent (at. %) to 10 at. %, specifically 1 at. % to 5 at.
%, and more specifically 3 at. % to 5 at. %, based on the total
weight of the alloy, with the balance being iron. In an embodiment,
the Fe--Mn binary alloy contains 4 at. % manganese, based on the
total weight of the alloy, with the balance being iron. Fe--Mo
binary alloy contains molybdenum in an amount from about 1 at. % to
about 10 at. %, specifically about 2 at. % to about 10 at. %, and
more specifically about 2.5 at. % to about 5 at. %, based on the
total weight of the alloy, with the balance being iron. In an
embodiment, the Fe--Mo binary alloy contains about 5 at. %
molybdenum, based on the total weight of the alloy, with the
balance being iron.
[0029] The Fe--V binary alloy contains vanadium in an amount from
about 2 at. % to about 22 at. %, specifically about at. % to about
20 at. %, and more specifically about 8 at. % to about 20 at. %,
based on the total weight of the alloy, with the balance being
iron. In an embodiment, the Fe--V binary alloy contains about 20
at. % vanadium, based on the total weight of the alloy, with the
balance being iron.
[0030] In the binary alloy, the manganese, molybdenum, or vanadium
can be miscible in the iron so that a solid solution is formed in
the binary alloy. Alternatively, the manganese, molybdenum, or
vanadium can be partially insoluble in the iron. Under the latter
condition, the binary alloy can form two or more phases.
[0031] Moreover, the manganese, molybdenum, or vanadium is miscible
in a melt of the iron and is soluble in the solid binary alloy and
the oxide of the binary alloy, i.e., the binary alloy and its oxide
are solid solutions having a single phase.
[0032] The binary alloys can be produced by methods known in the
art for alloys. In an embodiment, selected amounts of the iron and
manganese, molybdenum, or vanadium are combined at a temperature
effective to produce a melt of the metals. The metals can be
combined and then melted, or a melt of the iron is combined with
the manganese, molybdenum, or vanadium. Alternatively, the binary
alloys can be prepared by depositing, implanting, or doping the
iron with the manganese, molybdenum, or vanadium.
[0033] The binary alloys have excellent properties for use as
electrical contacts.
[0034] The binary alloys can have a bulk resistivity of less than
or equal to 500 nano-ohm-meters (n.OMEGA.-m), specifically 25
n.OMEGA.-m to 500 n.OMEGA.-m, 50 n.OMEGA.-m to 500 n.OMEGA.-m, 25
n.OMEGA.-m to 350 n.OMEGA.-m, or 50 n.OMEGA.-m to 350
n.OMEGA.-m.
[0035] Binary alloys having the foregoing compositions can form a
conductive oxide. Thus in another embodiment, a composition
comprises a binary alloy and a conductive oxide of the binary
alloy, specifically a conductive oxide formed from the binary
alloy. As used herein, "an oxide" or "the oxide" includes multiple
oxides, if multiple oxides are formed.
[0036] In the conductive oxide, the manganese, molybdenum, or
vanadium has a higher valence than the iron cations in the
conductive oxide. The oxide exists in a separate phase (or phases)
from the binary alloy. The oxide is formed on and in direct contact
with a surface of the alloy and may partially or completely cover
the surface. The binary alloy can be oxidized on a surface of the
alloy, or oxidation can penetrate into the bulk material of the
binary alloy. The conductive oxide can have one or more separate
phases. Alternatively, the conductive oxide can be present as a
single phase on the surface of the binary alloy or can penetrate
into the bulk of the alloy. In an embodiment, the composition
comprising the binary alloy and the conductive oxide of the binary
alloy is in the form of a solid solution binary alloy with an oxide
phase as a film on and in contact with the surface of the binary
alloy.
[0037] FIG. 1 is a cross-section of an embodiment of a binary alloy
with a passivating conductive oxide scale on the surface of the
binary alloy. Iron and manganese, molybdenum, or vanadium form a
single-phase binary alloy 101 denoted as Fe--X. Oxidation of the
binary alloy 101 forms a corresponding single-phase oxide 102
denoted as (Fe,X).sub.3O.sub.4. The atoms in the oxide 102 are
primarily present as ions of Fe.sup.2+, Fe.sup.3+, O.sup.2-, and
cations of X. The cations of X can have various oxidation states.
For example, if X is vanadium the cations of X can be V.sup.4+ or
V.sup.5+. For convenience, the cations of X are referred to as
X.sup.+ even when more than valence can occur. As shown, the oxide
102 is conductive. The thickness D of the conductive oxide 102 is
not particularly limited, and can be, for example, 0.5 nm to 100
nm, specifically 1 nm to 50 nm, and more specifically 1 nm to 10
nm.
[0038] The foregoing is merely illustrative of the form of the
compositions comprising the binary alloys and the conductive oxides
of the binary alloys. However, other configurations of the binary
alloys and conductive oxides can exist independently or together
with the configuration of the embodiment shown in FIG. 1.
[0039] Without being bound to any particular theory, the enhanced
conductivity of the compositions comprising the binary alloys and
the conductive oxides of the binary alloy can be ascribed to
electron/polaron hopping. FIGS. 2A, 2B, and 2C show a model of
electron/polaron hopping in an embodiment of a conductive oxide
film of a binary alloy. The underlying binary alloy contains iron
and manganese, molybdenum, or vanadium. In the conductive oxide
film 200, the crystal structure is an inverse spinel magnetite
(Fe.sub.3O.sub.4) in which iron exhibits ionic bonding as an
ensemble of divalent ferrous ions (Fe.sup.2+) 201 and trivalent
ferric ions (Fe.sup.3+) 202. The cations of the manganese,
molybdenum, or vanadium are present as, for example, tetravalent
(X.sup.4+) ions 203 in the oxide film 200. The tetravalent ions 203
substitute for trivalent iron ions 202. As indicated by the
straight arrows in FIG. 2B, the tetravalent ions 203 induce a
compensating change in the oxidation state of a neighboring iron
ion 202A from a trivalent valence (Fe.sup.3+) to a lower divalent
valence (Fe.sup.2+). The divalent ion on a trivalent ion site is a
polaron, which can enhance the conduction of the conductive oxide
film 200. As shown in FIG. 2C, the enhancement in conduction occurs
by electron/polaron hopping in which the polaron migrates on the
trivalent ion sublattice through electron exchange (shown by the
curved arrows) with adjacent iron ions in the divalent ion
sublattice. Thus, the oxide film 200 is appreciably conductive even
though the oxide for pure iron is not as conductive.
[0040] Further, for electron/polaron hopping, the bonding in the
conductive oxide of the binary alloy is predominantly ionic. It is
believed that the conductive oxide film of the binary alloy favors
induction of mixed valence states of the iron by the manganese,
molybdenum, or vanadium over the formation of oxygen vacancies
because the free energy for oxygen vacancy formation is
sufficiently large with respect to the energy required for
establishing mixed valence states for cations of the iron.
Additionally, the free energies of formation for the oxides of the
iron and the manganese, molybdenum, or vanadium of the binary alloy
are similar so that selective oxidation of either of the iron or
manganese, molybdenum, or vanadium is suppressed.
[0041] The foregoing is merely illustrative of one principle of
forming conductive oxides from binary alloys of the embodiments.
However, other mechanisms can exist and, independently or together
with the above-described mechanisms shown in FIG. 2, can modulate
the conduction of the conductive oxides.
[0042] The conductive oxides of the binary alloys can be formed by
a variety of processes, including exposure of the binary alloy to
ambient conditions, e.g., during use in the atmosphere at ambient
levels of humidity. The oxides can be formed under more oxidative
conditions and as part of a more aggressive processing procedure.
For example, the oxides can be formed by subjecting the binary
alloy to a thermally oxidizing or reducing atmosphere; treatment
with microwaves, electron beams, or X-rays; chemical treatment in
an oxidizing or reducing environment; and the like.
[0043] As stated above, the oxides of the binary alloys are
conductive. For example, the contact resistance of the composition
comprising the binary alloy and the conductive oxide can be less
than or equal to 5.times.10.sup.4 milli-ohms (m.OMEGA.).
[0044] The binary alloys can be used in a variety of applications
that use a conductive metal, for example, as electrical contacts
for electronic devices. An electrical contact formed using the
binary alloys can be used in a device before or after oxidation of
the binary alloy. Electrical devices generally include a first
component and a second component in a spaced apart relation. The
binary alloy (or the composition comprising the binary alloy and a
conductive oxide of the binary alloy) is disposed between and in
physical contact with the first component and the second component
to form an electrical path between the first component and the
second component. The binary alloy or composition thereof with a
conductive oxide of the binary alloy can be in a wide variety of
forms as needed to contact the first and the second component. The
form may be, for example, a wire, cable, button, coating, and the
like.
[0045] In an embodiment, the binary alloy or composition thereof
with a conductive oxide of the binary alloy is at least a portion
of a conductive contact in a connector, switch, or insert. Examples
of the connector are a blade connector, push-on connector, crimp
connector, multi-pin connector (e.g., a D-sub connector), bolt
connector, set screw connector, lug, wedge connector, bolted
connector, compression connector, coaxial connector, wall
connector, surface mount technology (SMT) board connector, IPC
connector, DIN connector, phone connector, plastic leaded chip
carrier (PLCC) socket or surface mount connector, integrated
circuit (IC) connector, ball grid array (BGA) connector, staggered
pin grid array (SPA) connector, and bus bar connector. Switches
include, for example, a circuit breaker, mercury switch, wafer
switch, dual-inline package (DIP) switch, reed switch, wall switch,
toggle switch, in-line switch, rocker switch, microswitch, and
rotary switch. An insert can be, for example, a transition washer,
disc, and tab.
[0046] In an embodiment, a connector includes a metal substrate
having a coating comprising the binary alloy or composition thereof
with a conductive oxide of the binary alloy disposed on a surface
of the metal substrate such that they form an electrically
conductive path. A metallic member, e.g., a mate such as a pin
couples to the connector to be in electrical contact with the
binary alloy or composition thereof. An electric voltage or current
can be established by the coupling, and the binary alloy or
composition thereof is the conduction path between the metal
substrate and the metallic mate.
[0047] In another embodiment, a switch includes a metal substrate
having the binary alloy or composition thereof with a conductive
oxide of the binary alloy disposed on a surface of the metal
substrate, to establish an electrically conductive contact. A
metallic member, e.g., a pole, couples with the binary alloy or
composition thereof of the contact. As a result of this coupling,
an electrically conductive path is established between the metallic
pole and the contact, with the binary alloy or composition thereof
being the conduction path between the metal substrate and the
metallic pole.
[0048] The binary alloys and compositions comprising the binary
alloys and the conductive oxides of the binary alloy have a number
of advantages. The oxidized portions of the binary alloys have
sufficient conductivity to prevent the development of an
unacceptably high contact resistance. Their use can decrease the
use of precious metal plating of electrical contacts while
conserving the operational characteristics of such current-carrying
contacts. In addition, the alloys are readily manufactured from
widely available materials.
[0049] The binary alloys and compositions comprising the binary
alloys and the conductive oxides of the binary alloys are further
illustrated by the following examples, which are non-limiting.
EXAMPLES
[0050] In the following examples, arc-melted ingots of the binary
alloys were used, and, where necessary, the ingots were
heat-treated to produce homogeneous microstructures on the length
scales relevant to contact applications, e.g., 10.sup.-4 meters (m)
to 10.sup.-2 m. The microstructures of the binary alloys and their
conductive oxides were characterized by X-ray diffraction (XRD),
scanning electron microscopy (SEM), and transmission electron
microscopy (TEM). Electrical data were obtained using 2-probe
4-point methods for bulk conductivities and a single-point
hemispherical gold probe for contact resistance per ASTM B667-97
(2009), "Standard Practice for Construction and Use of a Probe for
Measuring Electrical Contact Resistance." Contact resistances were
measured for freshly prepared alloy surfaces and for surfaces
exposed to air at 100.degree. C. for various times as noted
below.
[0051] An Fe--V binary alloy containing 8 at. % vanadium and the
remainder iron was oxidized by exposure to air at 100.degree. C.
for various times to form a conductive oxide on the surface of the
alloy.
[0052] FIG. 3 is a secondary electron scanning electron microscope
image of the Fe-8 at. % V alloy. The Fe-8 at. % V alloy has a
single phase with a grain size of greater than 200 micrometers with
a resistivity of 301.7 n.OMEGA.-m as compared to 102.5 n.OMEGA.-m
for high-purity iron.
[0053] FIG. 4 is a graph of relative intensity (arbitrary units,
a.u.) versus scattering angle (degrees, 2.theta.) data from an XRD
pattern of an oxidized Fe-8 at. % V alloy, and FIG. 5 is an
electron diffraction (ED) pattern of the oxidized Fe-8 at. % V
alloy. The XRD data in FIG. 4 contain only Fe and V peaks (labeled
as "a" at approximately 45.degree. and 65.degree.) from the
body-centered cubic Fe-8 at. % V alloy phase, and the ED data in
FIG. 5 establish that the oxides from the oxidized Fe-8 at. % V
alloy correspond to Fe.sub.3O.sub.4 rather than Fe.sub.2O.sub.3,
with no evidence for phase separation in the oxide. Therefore, the
oxide is a single phase with vanadium substitutionally incorporated
into the Fe.sub.3O.sub.4 lattice. The resolved diffraction rings in
FIG. 5 correspond to the {440}, {511}, {400}, {311}, and {220}
planes of the amorphous Fe.sub.3O.sub.4 crystal structure.
[0054] FIG. 6 is a graph of contact resistance (milli-ohms,
m.OMEGA.) versus oxidation time (hours, hr) for a copper sample, an
iron sample, and the Fe-8 at. % V alloy. The oxidized Fe-8 at. % V
alloy has a contact resistance that is 1.5 orders of magnitude less
than that for pure Fe and four orders of magnitude less than that
for pure Cu after air exposure at 100.degree. C. for 100 hours.
[0055] The temporal variation in surface resistivity due to
enhanced oxide film conductivity of the oxidized Fe-8 at. % V alloy
is due to substitutional V.sup.4+ or V.sup.5+ inducing a change in
the relative amount of Fe.sup.2+/Fe.sup.+ in the oxide film. The
mechanism for enhanced oxide film conduction is likely
electron/polaron hopping as illustrated in FIG. 2.
[0056] Although data shown in FIGS. 3, 4, 5, and 6 are for 8 at. %
vanadium in iron, additional embodiments can be produced having
other atomic percentage values of V in Fe that produce lower
contact resistance after oxidation as compared with oxidized Cu or
oxidized Fe.
[0057] Phase diagrams for compositions of iron with vanadium,
manganese, and molybdenum are respectively shown in FIGS. 7, 9, and
11. In addition to the Fe--V system, manganese and molybdenum
exhibit solubility in iron. Further, as with vanadium, manganese
and molybdenum may have different oxidation states such that each
can form a conductive oxide with iron.
[0058] FIG. 7 is a phase diagram of temperature (degrees Celsius,
.degree. C.) versus weight percent V (wt. % V) and atomic percent V
(at. % V) for an Fe--V system. Vertical dashed lines indicate
alloys of iron with 4 at. % V, 8 at. % V, 12 at. % V, 16 at. % V,
and 20 at. % V, which have solid states for each composition below
about 1538.degree. C. and a liquid state above this temperature.
Based on the phase diagram shown in FIG. 7, from a melt of iron and
vanadium, an alloy of a single phase .alpha.(Fe,V) can be formed
below about 1480.degree. C. for about 2 at. % V to about 22 at. % V
in a balance of iron.
[0059] FIG. 8 is a graph of contact resistance (milli-ohms,
m.OMEGA.) versus oxidation time (hours, hr) for a conductive oxide
of an Fe-4 at. % V alloy, Fe-8 at. % V alloy, Fe-12 at. % V alloy,
Fe-16 at. % V alloy, and Fe-20 at. % V alloy and comparative
results for copper and iron samples. As described above for Fe-8
at. % V, these additional conductive oxides of Fe--V alloys exhibit
surprisingly low contact resistance as compared to either copper or
iron and show about a 5 to about 20 times reduction in the contact
resistance with respect to iron after 400 hours of heating.
Similarly, the conductive oxides show about a 1000 to about 5000
times reduction in contact resistance with respect to copper after
400 hours of heating.
[0060] FIG. 9 is a phase diagram of temperature (degrees Celsius,
.degree. C.) versus weight percent Mn (wt. % Mn) and atomic percent
Mn (at. % Mn) for an Fe--Mn system. The vertical dashed lines in
the lower left-hand portion of the graph in FIG. 9 indicate alloys
of iron with 1 at. % Mn, 2 at. % Mn, 3 at. % Mn, 4 at. % Mn, and 5
at. % Mn, which have solid states for each composition below about
1800.degree. C. and a liquid state above this temperature. Based on
the phase diagram shown in FIG. 9, from a melt of iron and
manganese, an alloy of single phase .gamma.(Fe, Mn), for example,
can be formed below about 1650.degree. C. for about 1 at. % Mn to
about 10 at. % Mn in a balance of iron.
[0061] FIG. 10 is a graph of contact resistance (milli-ohms,
m.OMEGA.) versus oxidation time (hours, hr) for a conductive oxide
of an Fe-1 at. % Mn alloy, Fe-2 at. % Mn alloy, Fe-3 at. % Mn
alloy, Fe-4 at. % Mn alloy, and Fe-5 at. % Mn alloy and comparative
results for copper and iron samples. As shown in FIG. 10, these
conductive oxides of the Fe--Mn alloys exhibit surprisingly low
contact resistance as compared to either copper or iron. The data
for the conductive oxides show about a 5 to about 19 times
reduction in the contact resistance with respect to iron after 400
hours of heating. Similarly, they show about a 1300 to about 5000
times reduction in contact resistance with respect to copper after
400 hours of heating.
[0062] FIG. 11 are phase diagrams of temperature (degrees Celsius,
.degree. C.) versus weight percent Mo (wt. % Mo) and atomic percent
Mo (at. % Mo) in an Fe--Mo system. FIG. 11A has a vertical dashed
line that indicates the temperature-dependent phase of an Fe-5 at.
% Mo alloy. FIG. 11B, which shows an enlarged portion of the phase
diagram shown in FIG. 11A, has vertical lines that depict similar
information for an Fe-1 at. % Mo alloy, Fe-2 at. % Mo alloy, Fe-3
at. % Mo alloy, and Fe-4 at. % Mo alloy, which have solid states
for each composition below about 1450.degree. C. and a liquid state
above about 1540.degree. C. Based on the phase diagram shown in
FIG. 11, from a melt of iron and molybdenum, an alloy of single
phase .alpha.(Fe), for example, can be formed below about
1500.degree. C. for about 1 at. % Mn to about 4 at. % Mn in a
balance of iron.
[0063] FIG. 12 is a graph of contact resistance (milli-ohms,
m.OMEGA.) versus oxidation time (hours, hr) for a conductive oxide
of an Fe-1 at. % Mo alloy, Fe-2 at. % Mo alloy, Fe-3 at. % Mo
alloy, Fe-4 at. % Mo alloy, and Fe-5 at. % Mo alloy and comparative
results for copper and iron samples. As shown in FIG. 12 these
conductive oxides of the Fe--Mo alloys exhibit surprisingly low
contact resistance as compared to either copper or iron and
generally have a decreasing contact resistance with an increasing
amount of Mo. The data for the conductive oxides show about a 4 to
23 times reduction in the contact resistance with respect to iron
after 400 hours of heating. Similarly, they show about a 700 to
about 4300 times reduction in contact resistance with respect to
copper after 400 hours of heating.
[0064] The singular forms "a," "an," and "the" include plural
referents unless the context clearly dictates otherwise.
[0065] Various numerical ranges are disclosed in this patent
application. Because these ranges are continuous, they include
every value between the minimum and maximum values. The endpoints
of all ranges reciting the same characteristic or component are
independently combinable and inclusive of the recited endpoint.
[0066] Elements and compounds are described herein using standard
nomenclature.
[0067] All references are incorporated herein by reference.
[0068] While the invention has been described with reference to
various embodiments, it will be understood by those skilled in the
art that various changes can be made and equivalents can be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications can be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to any
particular embodiment disclosed for carrying out this invention,
but that the invention will include all embodiments falling within
the scope of the appended claims.
* * * * *